Investment casting is an industrial process based on one of the oldest metal forming techniques. This process is capable of producing complicated shapes that would be difficult or impossible (particularly with high melting temperature alloys) with die casting. Investment casting produces parts that usually require little surface finishing and only minor machining Usually, the process begins with fabrication of a sacrificial ceramic pattern with the same basic shape as the finished cast part. Patterns are made wax that is injected into a metal injection die. Fabricating the injection die is expensive and can take months of lead time.
Once a wax pattern is produced, it is then dipped in a ceramic slurry, covered with a particulate material, and allowed to dry. Once dried, the pattern is placed in an autoclave to remove the wax. After autoclaving, any remaining wax is burned out in a furnace during which the ceramic shell is also hardened. The mold is then preheated and filled with molten metal, creating the metal casting. Once the casting has cooled sufficiently, the mold shell is chipped away from the casting.
Die casting, on the other hand, is the process of forcing molten metal under high pressure into mold cavities that are machined into dies. Most die castings are made from nonferrous and relatively low melting temperature metals specifically zinc, copper, aluminum, magnesium, lead, and tin-based alloys, although ferrous metal die casts are possible. After the die is filled, and the material therein has solidified, the part for casting is ejected usually by ejector pins. Thereafter, any scrap, which includes gate runners and flash etc. must be separated from the castings.
The dies used in die casting are usually made out of hardest tool steels because cast iron cannot withstand the high pressures involved. Due to this, dies are expensive and may have high start-up costs.